Thermal relay



Aug- 9 1932 w. M. ELLINGsoN 1,871,262

THERMAL RELAY Filed oct. 50,*1931 47`. 21s za 68 WITNESSES:

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f/v BY ATTORNEY INVENTOR Patented Aug. 9, 1932 UNITED STATES PATENT OFFICE WILLIAM M. ELLINGSON, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTING` HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION E PENNSYL- VANIA.

THERMAL RELAY Application filed October 30, 1931. Serial No. 572,107.

My invention relates to relays and particularly to thermal relays. v

An object of my invention is to provide a relatively simple, highly efficient means, easily manufactured and installed in a thermal relay, for effecting selective operation thereof at different operating current values.

In practicing my invention, I provide a thermal relay including an energizing coil, a magnetizable frame structure including a movable armature portion and a heated member having a thermally variable magnetic characteristic normally engaged by the movable ,armature and effective to cause movement thereof at predetermined current and time conditions of the relay. The thermally variable magnetic `member consists of a plurality of portions having different temperature values at which the parts lose their magnetic characteristic.

In the single sheet of drawing,

Figure 1 is a view, in front elevation, of a specific form of thermal relay in which is embodied the device particularly constituting my invention.

Fig. 2 is a view in vertical section therethrough taken on the line II-II of Fig. 1, an

Figs. 3 to 8, inclusive, are front elevation and top plan views of various modifications of a device embodying my invention.

A thermal relay is mounted on a suitable base 11 which is preferably, although not necessarily, made of a suitable electric-insulating material.

An energizing coil 12 is provided for the relay, as shown in the drawing, the same being illustrated as a series coil made up of a plurality of spaced turns of flat metal strip bent on edge. One terminal of the coil is connected to the forward end of a terminal stud 13 which is extended through the base 11. The other end of the coil 12 is locatednearthe front surface of the base 11, and

: includes a bent portion 14 extending forwardly parallel to the axis of the coil.

The coil 12 is provided with a core 16 which may be surrounded by a tubular bushing 17 of electric-insulating material and may beheld against the front surface of the base 11 by a bolt 18. The bolt 18 is effective also to hold'or clamp a rear yoke 19, of substantially L-shaped magnetizable material, against the base.

The frontend of the core 16 carries a magnetizable front bracket 21, secured by a bolt 22 and comprising a short, straight, flat bar of iron or steel. The top of this front bracket carries a magnetizable armature-support 23, of substantially L-shape, which has one of its legs secured against the front bracket by means of a plurality of machine screws 24 extending through an elongated lateral slot 26 in the supporting member 23.

The upper or horizontal leg of the angular support 23 carries a longitudinally adjustable and pivotally mounted armature 27, which may be a substantially fiat bar, aknife edge 28 being provided on the supporting member 23 for this purpose, and the movable armature 27 having two cooperating recesses 29 for selectively fitting over the knife edge. The armature 27 is yieldably maintained in its initial lowermost position by a pin 31 which is fixed in the supporting member 23 and which is surrounded by a spring 32 cooperating with a washer 33 and a cotter pin 34.

Under the rear end of the pivoted armature 27 is a bar or strip 36 of a thermally responsive magnetically-reversible metal, of novel construction as will be hereinafter described in greater detail, which extends parallel to the front face of the base 11 and has one of its ends electrically connected to the horizontally extending bent rear-end portion 14 of the coil 12, as by means of a bolt 37 having a nut 38 thereon. The other end of the magnetically reversible bar 36 is supported by a terminal strip 39, as shown more particularly in Fig. 1 of the drawing, the upper end ofwhich is provided with a forwardly extending portion and the ldwer end of which is connected to a terminal stud 41 substantially the same as stud 13. A bolt 42 and a nut 43 thereon effect electrical connection of the magnetically reversible strip 36 and the terminal strip 39.

In order to ensure a greater rigidity of the electric coil structure, and to carry the fiux stantiauy 35% yfrom the yoke 19 to the magnetically reversible bar 36, I provide two angle-iron brackets 44 and 46 (Fig. 1) having forwardly extending flanges 47 (Figs. 1 and 2) secured to opposite ends of the bar and to the terminals 14 and 39, respectively, by the aforementioned bolts 37 and 42. Each of the brackets 44 and 46 is secured against the base 11 by machine screws 48.

It may be noted that the rear end of the movable armature 27 is located between/a forwardly extending flange or pole-piece 51 of the magnetizable yoke member 19 and the magnetically reversible bar 36. This bar 36 is preferably made of a nickel-steel alloy, or its equivalent, which has a thermally variable magnetic characteristic. Thus, if a nickel steel alloy is used, having substantially 35% of nickel, it is normally magnetic or magnetizable at all temperatures up to about 210O C. At a temperature of approximately 210o C., it loses its magnetic characteristic only to regain the same when cooled again to a temperature below approximately 210 C. A member of this kind may be said to have a thermally variable magnetic characteristic or to be a magnetically reversible member.

It is obvious that it is not necessary that the magnetically reversible member` 36 be directly traversed by the relay current, as it may be heated indirectly by an electric resistor which is traversed by the relay current to be controlled. i

A controlled means is illustrated in the drawing as including a switch-arm 52 normally yieldingly maintained in engagement with a fixed contact terminal 53, the switcharm 52 being pivotally mounted on a terminal member 54 and biased toward closed position by a spring 56 cooperating with the terminal member 54. The switch-arm is opened by a push-rod 57 which moves upwardly in a guide 58 when the pivoted armature 27 is released by the magnetically reversible rod 36. To this end, a striking plate 59 is riveted to the-rear end of the armature 27, to engage the lower end of the push-rod While I have described a specific embodiment of a thermal-relay switch, I desire it to be understood that these parts constitute no part of my present invention, which resides more particularly in the details of construction of the magnetically reversible member 36, as will now be described in detail.

Referring, for instance, to Figs. 3 `and 4 of the drawing, I have there illustrated a composite bar or strip 36 whigli includes two series-related portions 63 and 64, having different critical temperatures, as previously described, the adjacent end portions are welded together as by a seam 66 of welding metal. The portion 63 may be of the composition hereinbefore of nickel, the remainder being set forth, including subprincipallyl iron. rlhe portion 64 may be an alloy including a somewhat higher percentage of nickel, so that the temperature at which it will lose its magnetic characteristic will be somewhat higher than 210 C. as, for instance, 240O C. If a current of predetermined value traverses the strip 36 and if this current is of such value,y as to cause the low-nickel portion l63 to lose its magnetic characteristic after the current has traversed the strip for a predetermined length of time, it is obvious that the high-nickel portion 64, if of the sameyarea of cross section as the lownickel portion 63, will be heated to the same temperature, which is lower than the critical temperature of the high-nickel portion 64. Therefore, a higher current will be required to cause the high-nickel portion 64 to lose its magnetic characteristic.

Reference to Fig. 2 of the drawing will show that there is a divided magnetic circuit for the flux generated by the energizing coil 12. One of the two parallel-related paths is from the yoke member 19, which carries substantially all of the flux of the magnet-core 16, to the top flange or pole-piece 51 thereof which, in cooperation with the armature 27, may be said to constitute a pull-in portion. The second and parallel-related path from the yoke 19 is through the forwardly extending parts 47 of the iron aprons 44 and 46, and thence through the magnetically reversible member 36, which may be said to constitute a hold-out portion. Thus, if the armature 27 is biased, as by gravity or the spring 32, into engagement with the magnetically reversible bar 36, it will be held there by the attraction of the bar, against the attraction of the pole-piece 51, until the bar loses enough of its magnetic properties because of rise of temperature thereof, when the magnetic flux in the upper yoke-flange or pole-piece 51 will cause an upward movement of the-armature, elevating the push-rod 57 and thus effecting the opening of the switch-arm 52.

Referring to Fig. 4 of the drawing, I have shown how it is possible to accentuate the difference in the critical currents at which the two strip-portions 63 and 64 respond, by

varying the area of cross section, although this particular detail constitutes no part of my present invention, aside from its use in combination with a composite-strip construction. It will be obvious that the reduction of the area of the low-temperature portion 63 will make it reach its critical temperature sooner than the tion 64.

Referring to Fig. 5 of the drawing, I have there illustrated a composite member 36a including four different nickel-steel alloys. comprising portions 68, 69, 71 and 72 which are connected in series relation both mechanically and electrically by a plurality of seems 73 of welding metal. It is to be underhigh-temperature porstood that the temperatures at which the portions 68, 69, 71 and 72 lose their magnetic characteristic will be different andVmay be progressively different.v

Referring to Fig. 6 of the drawing, I have illustrated the magnetically reversible bar 36?; as being composed of two parallel-related portions 74 and 76 united by a longitudinal seam 77, the temperatures at which they lose their magnetic characteristic being different. p In Fig 7 of the drawing, I have illustrated @somewhat similar composite strip 36e including a portion 79 and a 'parallel-related portion 81, each of which may include a laterally deformed mid-portion.

In 8 of the drawing, I have illustrated a somewhat different joint between two portions 82 and 83, which joint extends angularly across the composite strip.

Itis obvious that it is only necessary to move the armature 27 laterally, relatively to the .front supporting-bracket 21, as by loosrvening the machine screws 24, in order that the point of engagement between the rear end of the armature 27 and the composite strip 36 may be moved longitudinally of the strip, as will be proper for the strips shown in Figs 4, 5, 7 and 8, as indicated by the bro- ,ken line circles. `The provision of a pair of recesses 29 in the armature 27 for selectively engaging the knife-edge support 28 will permit the armature 27 to be moved in a direction laterally of the strip 36, as/will be proper for the embodiment. shown in Fig.-6 of the drawing. The broken line circles on the members shown in Figs 3 to 8 indicate the positions of the head of a rivet 84 (Fig. 2) extending through the armature 27 and striking the f strip 86. Where two portionsA are shown for the composite strip, it is obvious that the relay can be adjusted for two diii'erent operating values of current traversing the relay, while a larger number of such operating current values may be obtained by the use of the composite bar shown in Fig. 5 of the drawing.

My invention thus provides a means, in a thermal relay for causing the armature to be actuated from its normal position to its operated position ata plurality of different current-time values, which adjustment is effected by relatively simple mechanical means. It may be noted particularly that, when the electrical connections to the thermally variable magnetlc member 36 have once been effected, they are not thereafter disturbed, as it is only necessary to move a small portion of the magnetic circuit structure of`the relay.

Various modifications may be made in my invention without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior artor are set forth in the appended claims.

I claim as my invention:

1. Ina thermal relay having an energizing coil and an armature movable relatively to the coil, means for eifectingselective control of the armature at different values of current traversing the relay, including a heated plural-part member having different thermally-variable magnetic characteristics in the` different parts thereof.I

2. In a thermal relay having an energizing coil and anl armature movable relatively to the coil, means for effecting selective control ot the armatureat different values of current traversing the relay, including a heated pluent values of relay current, said means including a plural-part heated member, each part being magnetically-reversible at a different temperature.

' 4. In a thermal relay having an energizing coil and an armature movable relatively to vthe coil, means for eifecting selective operation of the armature at different values of current traversing the relay, said means including a plural-part heated member, each part of the member being magnetically reversible at a different temperature, and'means for eii'ecting selective engagement of the armature with the different parts vof the heated member.

5. A thermal relay having a core, an energizing coil, an armature movable relatively to the coil and core, a support for 'the armature, means normally in engagement with and holding the armature in a predetermined position and effective to selectively release the same at different values of current traversing the relay, said means including a plural-part heated member, each part being magnetically-reversible at a different temperature, and means cooperating with the armature and itssupport to eect selective engagement of the armature with the different parts of the heated member.

6. A thermal relay having a core, an ener-` gizing coil, an armature movable relatively :to thecoil and core a support for the armature, means normally in engagement with and holding the armature in a predetermined position and ,effect-ive to selectively release the same at'` different values of current traversing the relay, said means including a plural-part current-traversed bar, each part of the bar being magnetically-reversible at progressively different temperatures, and means for effecting movement of the armature relatively to its support to cause engagement thereof with selected parts of the cur- Y rent-traversed. bar.

7. A thermally-responsive electric relay comprising a bar of thermally variable, magnetically-reversible material, means for generating heat for heating said bar in ac- 5 cordance with the current traversing said relay, a movable armature normally attracted by said bar when the latter is cold, magnetizing means for magnetizing said armature and tending to attract it away from l@ said bar, and means tor adjusting the point on the bar which attracts the armature, said 'barfbeing composed of a plurality of pieces of different thermally variable, magneticallyreversible alloys having dierent critical temperatures at which they have a sharp vbreak in their permeability-temperature characteristics. l

8. A thermally-responsive electric relay comprising a bar of thermally variable, 2c magnetically-reversible material, means tor generating heat tor heatingvsaid bar in accordance with the current'traverbsing said relay, a movable armature normally attracted by said bar when the latter is cold, magnetizing means for magnetizing said armature and tending to attract it away vfrom said bar, and means for adjusting the point on the bar which attracts the armature, said bar being composed of a plurality of pieces 3,0 of different thermally variable, magneticallyreversible alloys having different critical temperatures at which they have a sharp break in their perme'ability-temperature characteristics, said pieces being so disposed that a plurality of longitudinally spaced points along the length of the bar lose their magnetism suiiiciently to release the armaturev at dilerent currents and/or times of rcurrent-flow, and means for adjustably sup- 40 porting the armature so that it may beselectively attracted by any one of said points.,

9. A thermally-responsive electric relay `comprising a bar of thermally variable, magnetically reversible material, -means for generating heat for heating said bar in accordance with the current traversing said relay, a movable armature normally attracted byv said bar when the latter is cold, said armature beingeat substantially right angles with respect to said bar, magnetizing means for magnetizing said armature and tending to attract it away from said bar, and means for adjusting the point on the bar which attracts the armature, said bar being composed of a .plurality of pieces of dil'erent thermally variable, magnetically-reversible alloys having different critical temperatures at which they have a sharp break in their permeability-temperature characteristics, said pieces being so disposed that a plurality of longitudinally spaced points along the length of the bar lose their magnetism sufti ciently to release the armature at 'different currents and/or times of current-How, and an adjustable supporting bracket for the narines vmovable armature, whereby the armature and its support may be moved bodily in a lateral direction so that the armature may be selectively attracted by any one` ot said points.

l0. A thermally-responsive electric relay comprising a bar of thermally variable, magnetically-reversible material, means for generating heat for heating said bar in accordance with the current traversing said relay, a movable armature normally attracted by said bar when the latter is cold, magnetizing means for magnetizing said armature and tending to attract it away from said bar, and means for adjusting the point on the bar which attracts the armature, said bar being composed of a plurality of pieces of different thermally variable, magnetically-reversible alloys having diderent critical temperatures 'at which they have a sharp break in their permeability-temperature characteristics, said pieces being so disposed that a plurality of laterally spaced point-s across the width of the bar lose their magnetism sutliciently to release the Varmature at dierent currents and/or times of currentsllow, and means for adjustably supporting the armature so that it may be selectively attracted by any one of said points.

l1. A thermally-responsive electric relay comprising a bar of thermally variable, magnetically-reversible material, means for generating heat for heating said bar in accordance with the current traversing said relay, a

movable armature normally attracted by said bar when the latter is cold, said armature bein'g at substantially right angles with respect to said bar, magnetizing means for magnetizing said armature and tending to attract it away from said bar, and means for adjusting the point on the bar which attracts the armature, said bar being composed of a plurality of pieces of different thermally variable,mag

vnetically reversible alloys having different critical temperatures at which they have a sharp break in their permealility-temperature characteristics, said piece being so disposed that a pluralty of laterally spaced points across the width of the bar lose their magnetism suliiciently to release the armature at di ferent currents and/or times of currentflow, and means for adjusting the pivotal point of the moving armature longitudinally with respect to the armature, whereby the armature may be selectively attracted by anyi one of said points.

12. A thermally-responsive electric relay comprising a bar of thermally variable, magnetically reversible material, means for generating heat for heating said bar in accordance with the current traversing said relay, a movable armature normally attracted by said bar when the latter is cold, said armature being at substantially right angles with respect to said bar, magnetizing means for dinally along the length of said bar, the bar being such that diilerent points along its length lose their magnetism sufficiently to release the armature at different currents and/or times of current-flow.

13. A thermally responsive electric relay" comprising a bar of thermally variable, magnetically-reversible material, means for generating heat for heating said bar in accordance with the current-traversing said relay, a movable armature normally attracted by `said bar when the latter is cold, said armature being at. substantially right angles with respect to said bar, magnetizing means for magnetizing said armature and tending to attract it away from said bar, and means for adjusting the pivotal point of the moving armature longitudinally with respect to the armature, whereby the armature is adjusted laterally with respect to said bar, the bar being such that different points across its width lose their magnetism suticiently torelease the armature at difl'erent currents and/or times of current How.

14. The invention as specified in claim 13, characterized by a plurality of transverse grooves, on the side of the armature adjacent to the bar, a knife-edge support for selectively engaging any of said groves, and spring means for yieldably holding said knife-edge support in its selected groove and for biasing the armature toward said bar.

15. A thermal relay comprising a currenttraversed bar of thermally variable, magnetically-reversible material heated by the traversing current, a movable armature normally attracted by said bar when the latter is cold, magnetizing means for magnetizing said armature and tending to attract it away from said bar, and means for adjusting the point on the bar which attracts the armature, said bar being composed of a plurality of pieces of different thermally variable magnetically reversible alloys having dierent critical temperatures at which they have a sharp break in their permeability-temperature characteristics.

16. A thermal relay comprising a currenttraversed bar of thermally variable, :magnetically-reversible material heated by the traversing current, a movable armature normally attracted by said bar when the latteris cold, magnetizing means for magnetizing said armature and tending to attract it away from said bar, and means for adjusting the point on the bar which attracts the armature, said bar being composed of a plurality of pieces of different thermally variable, magnetlcally reversible alloys having different critical temperatures at which they have a sharp break in their permeability-temperature characterj istics, said pieces being'so disposed that a plurality of longitudinally spaced points along the length of the bar lose their magnetism suiiciently to release the armature at dilerent currents and/or times of currentflow, and means for adjustably supporting the armature so that it may be selectively attracted by any one of said points.

17. A thermal relay comprising a currenttraversed bar of thermally variable, magnetically-reversible material heated by the traversing current, a movable armature normally attracted by said bar When the latter is cold, magnetizing means for magnetizing said armature and tending to attract it away from saidbar, and means for adjusting the point on the bar which attracts the armature, said bar being composed of a plurality of pieces of different thermally variable, magnetically-reversible alloys having diilerent critical temperatures atwhich they h ve a sharp break in their permeabilityemperature characteristics, said pieces being so disposed that a plurality of laterally spaced points across the width of the bar lose their magnetism sufficiently to release the armature at diiijerent curents and/or times of currentflow, and means for adjustably supporting the armature so that it may be selectively attracted'by any one of said points.

18. The invention as defined in claim 16, characterized by said pieces being serially disposed and joined together at their abutting edges.,

19. The invention as deiinedin claim 16, characterized by said pieces being serially disposed and joined together at their abutting edges, said abutting edges being diagonally disposed.

20. The invention as defined in claim 17, characterized by said pieces being serially disposed and joined together at their abutting edges, said abutting edges being diagonally disposed.

21. The invention as defined in claim 17, characterized by said pieces being paralleldisposed strips.

22. rIhe invention as defined in claim 16, characterized by said pieces being paralleldisposed strips having their central portions doubly offset laterally in a reversed curve to bring portions of both strips into longitudinal alinement. p f

In testimony whereof, I have hereunto subscribed my name this 26th day yof October 

